The skeleton or frame structure of buildings of the general kind above referred to is generally erected by constructing upright steel beams or columns suitably anchored in a foundation or to each other when the height of the building requires more than one length of uprights. The horizontal or cross beams are secured to the uprights at levels selected in accordance with the desired number and height of the stories of the building. The cross beams are rigidly secured to the uprights by riveting, welding, use of ties and other fastening means customarily used in the building industry whereby the finished frame structure is essentially rigid in its entirety unless complex and expensive steps are taken to impart some elasticity to the joints. The uprights in the frame structure when the same is completed or as it is being erected, depending upon the desired final height of the structure, are sheathed with concrete which may or may not be reinforced. Such sheathing requires time consuling and hence expensive assembly and disassembly of molds in situ. It is also known to use pre-fabricated slabs but such slabs must be joined which also requires extensive assembly and disassembly of molds in situ.
As the finished building is essentially a rigid structure, heavy horizontal wind pressure and seismic shocks tend to cause cracks in the sheathing and possibly more extensive damage to the building such as partial or complete collapse if the seismic shocks are of great magnitude. Even if the building is not damaged by external forces, cracks tend to develop in the sheathing of the frame structure as the sheatings tend to settle and to contract or expand due to the influence of moisture and temperature.
Joining of the cross beams to the uprights by riveting, welding, use of ties, etc. is expensive and time consuling as it requires highly skilled labor, the more so, as the cross beams and the uprights generally do not fit perfectly but must more often than not, be carefully adjusted by use of ties and brackets. In Today's labor market the costs of erecting a building are primarily controlled by labor costs rather than by the costs of material. Hence, erection of a building, particularly of a high rise building with the methods now conventionally used for erecting such buildings is time consuming and is very often highly desirable for reasons other than costs that a building be completed as soon as possible.
Moreover, all stress and other calculations must be specifically made for each building and prefabricated components can generally be used only for one type of construction.